Composite material for geometric morphing wing

ABSTRACT

An airfoil member and an airfoil member altering system are provided for significantly modifying the shape and size of the airfoil member while simultaneously providing an airfoil member with increased adaptability to various flight conditions throughout a flight envelope. The airfoil member comprises at least one motor or actuator, a system controller, a plurality of vehicle performance sensors, at least one temperature controller and airfoil member comprising at least one geometric morphing device that is adjustable in both size and shape and one or more rigid members.

RELATED APPLICATION

This application is related to U.S. patent application (Attorney DocketNumber 02-1244, Ser. No. 10/357,022, filed Feb. 3, 2003) entitled “FiberMatrix for a Geometric Morphing Wing”, which is incorporated byreference herein.

FIELD OF THE INVENTION

This application relates generally to aeronautical vehicle systems, andmore particularly, to an apparatus, system, and method of altering thesize and shape of an airfoil wing member.

BACKGROUND OF THE INVENTION

Airfoil members such as wings, horizontal and vertical stabilizers,canards, rotor blades, winglets, etc. are limited in ability to changetheir sizes and shapes so as to alter surfaces of the airfoil member andbe adaptable to multiple flight conditions of a flight envelope.

Currently, airfoil member surfaces of an aircraft can be modified to acertain extent by various devices for improved flight characteristicssuch as during low-speed takeoff and descent, autopilot maneuvering, orfor high-speed aerodynamics. Aircraft that need to operate in severalperformance environments, however, often must compromise flightperformance by using airfoil members that do not provide suitablecharacteristics in multiple environments rather than using airfoilmembers that are specifically designed for a particular flightsituation.

Aircraft designs known today utilize a variety of airfoil member surfacemodifying devices such as, flaps, slats, flaperons, ailerons, splitailerons, or other leading or trailing edge devices known in the art, toprovide control forces and moments during flight. Also, other devicessuch as micro flow devices, zero mass jets, and the like are used tocontrol the airflow over the airfoil member to further control forcesand moments. Additionally, devices such as smart materials are used toslightly the modify shape of the airfoil member itself or of the airfoilmember surface modifying devices. However, all of there devices arelimited in their ability to alter shape, size, and characteristics ofthe airfoil member; the airfoil member devices typically only modify asingle aspect of the airfoil member, minimally affect airflow, orslightly modify shape of the airfoil member. Furthermore, all of theabove-stated devices tend to use motors or actuators and othermechanical components to perform minor changes in an airfoil surface.

Military aircraft have utilized mechanically swept wings for improvedaerodynamics during high-speed flight. These mechanical surface systems,however, typically only provide a very limited ability to affect airfoilmember shape and aerodynamic flight characteristics of the aircraft. Thelimited ability to significantly change airfoil member shape can resultin an airfoil member that is particularly suitable for only a limitedrange of a flight envelope.

It is therefore desirable to provide an airfoil member and an airfoilmember altering system that significantly modifies shape and size of theairfoil member and at the same time provides an airfoil member withincreased adaptability for various flight conditions throughout a flightenvelope. An airfoil member with improved adaptability may potentiallybe capable of supporting greater payloads at lower speeds and duringtake-off and landing of an aircraft, better aerodynamic characteristicsat high speed, and increased flight range.

The copending application Ser. No. 10/357,022 as referenced above, aswell as U.S. Pat. No. 6,786,457, teaches geometric morphing of anairfoil by changing the inflated state of the inflatable members in theairfoil.

SUMMARY OF THE INVENTION

This application describes an apparatus, system and method of alteringthe size and shape of an airfoil member. The airfoil member comprises atleast one motor or actuator, a system controller, a plurality of vehicleperformance sensors, at least one temperature controller, and an airfoilmember comprising at least one geometric morphing device that isadjustable in both size and shape and preferably one or more rigidmembers. The geometric morphing device comprises a fiber mesh, a matrixmaterial, four bars interconnected to wherein the fiber mesh isenclosed, and pins to each of which two adjacent bars are pivotallyconnected. The elastic properties of the airfoil matrix material aresusceptible to an external stimulus, preferably a change in itstemperature induced by cooling or heating the matrix material. When achange in the size and/or shape of at least a section of the airfoil isdesired, the temperature modulator coupled to the section of the airfoilis actuated and a change in the local temperature causes the matrixmaterial of the section to switch from a substantially stiff form to anelastically deformable form. The motor or actuator coupled to thesection of the airfoil is subsequently actuated to cause a change in theshape and/or size of the section of the airfoil. When the desired shapeand/or size have been achieved, the temperature modulator changes thetemperature and returns the section of the airfoil to a stiff form,locking it into the new shape and/or size.

This device has several advantages over existing airfoil member alteringdevices. One advantage is that an airfoil member is provided that iscapable of significantly changing its size and shape. Versatility of thedevice also allows shape of the airfoil member to alter in compoundmanners. The ability to significantly change in size and shape providesincreased application versatility and increased flight controlthroughout a flight envelope.

Another advantage is that it provides improved adaptability, improvedflight characteristics including supporting greater payloads at lowerspeeds, and during take-off and landing, better aerodynamiccharacteristics at higher speeds, and increased flight range incomparison with traditional airfoil member altering devices that arelimited in one or more of the above-stated characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective and schematic view of an aircraft that isutilizing an airfoil member altering system in accordance with a firstembodiment.

FIG. 2 is a plan view of the morphing device for use with the airfoilmember altering system in accordance with the first embodiment, beforemorphing is initiated.

FIG. 3 is a plan view of the morphing device for use with the airfoilmember altering system in accordance with the first embodiment, aftermorphing is finished.

FIG. 4 is a plan view of the morphing device for use with the airfoilmember altering system in accordance with the first embodiment, beforeand after morphing is conducted, wherein more than one bar is actuatedto achieve a more complex shape.

FIGS. 5A-5D are schematic views of additional configurations of morphedshapes for use with the airfoil member altering system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In each of the following figures, the same reference numerals are usedto refer to the same components. While this application describes anapparatus, system, and method of altering size and shape of an airfoilmember, the apparatus, system and method may be adapted for variousapplications including ground-based vehicles, aeronautical vehicles,including fixed wing and rotary wing aircraft, watercraft, and otherapplications known in the art that require the use of airfoil members.The apparatus, system and method may be applied to vertical stabilizersto increase control at lower speeds and to decrease drag at higherspeeds, to winglets for modifying flight speed, and as well as tohorizontal and canard surfaces. The apparatus, system and method may beapplied to flaps and ailerons to modify shape of an airfoil member. Theapparatus, system and method may also be used to modify flight controlby changing the size and shape of a first airfoil in a first manner andby maintaining a second wing in a current state or by changing the sizeand shape of the second airfoil in a second manner, thus causingrolling, pitching, or yawing moments.

In the following description, various operating parameters andcomponents are described for one constructed embodiment. These specificparameters and components are included as examples and are not meant tobe limiting.

Also, in the following description the term “morphing” refers to abilityof an object or device to change. The term “geometric morphing device”refers to the ability of a device to change in size and shape. Forexample, an airfoil member is capable of changing in size and shapewhere parameters including but not limited to span, chord, and camber ofthe airfoil member are adjustable.

Referring now to FIG. 1, a perspective and schematic view of an aircraft10 that is utilizing an airfoil member altering system 12 is shown. Theairfoil member altering system 12 may comprise at least one motor oractuator 20, a system controller 24, a plurality of vehicle performancesensors 28, at least one temperature controller 30, and an airfoilmember 14 comprising at least one geometric morphing device 40 that isadjustable in both size and shape and preferably one or more rigidmember 50.

A system controller 24 may be electrically coupled to the motor oractuator 20, a temperature controller 30, and to preferably one or moresensors 71 embedded in the morphing device 40 for monitoringtemperature, pressure, etc. The system controller 24 is alsoelectrically coupled to multiple aircraft devices including vehicleperformance sensors 28 and aircraft control inceptors (not shown). Thesystem controller 24 may be coupled to other aircraft devices and maydetermine the positions of the control inceptors for constant vehicleoperating states such as a constant altitude mode or constant velocitymode. The system controller 24 determines multiple size and shape of themorphing device 40 for multiple flight conditions throughout a flightenvelope.

The motor or actuator 20 is controlled by the system controller 24, andcoupled to the morphing device 40. Although only one motor or actuatoris shown, more than one motor or actuator can be employed for onemorphing device 40, especially when the shape/size of the morphingdevice needs to be controlled precisely or when a complex shape isdesired. In addition, more than one motor or actuator is preferably usedto independently control each of the morphing devices in the eventmultiple morphing devices are present.

A temperature controller 30 is controlled by the system controller 24,and coupled to at least one temperature sensor 61 embedded in themorphing device 40 and at least one heating/cooling element 62 embeddedin the morphing device 40. Of course, preferably more than onetemperature sensor 61 is used to provide a measurement of temperaturedistribution within the morphing device 40 and more than oneheating/cooling element 62 is used to provide a more precise and uniformtemperature shift within the morphing device 40. The system controller24 can also rely on the temperature sensor 61, via the temperaturecontroller 30, to acquire temperature of the morphing device 40, thusforgoing a directly connected temperature sensor in the one or moresensors designated by 71.

The system controller 24 and the temperature controller 30 may bemicroprocessor based such as a computer having a central processingunit, memory (RAM and/or ROM), and associated input and output buses.The system controller 24 and the temperature controller 30 may be aportion of a central main control unit, a flight controller, anintegrated controller, or may be stand-alone controllers as shown.

The vehicle performance sensors 28 may include vehicle external airpressure sensors, velocity sensors, acceleration sensors, momentsensors, altitude sensors, or other sensors known in the art. Thevehicle performance sensors 28 may determine a current velocity andacceleration of the aircraft 10, as well as determining a current momentabout a yaw heading or z-axis, a pitch or x-axis, and roll or y-axis.

The morphing device 40 comprises a fiber mesh 51, a matrix material 52,four bars 81, 82, 83 and 84 interconnected to form a rectangular shapewherein the mesh 51 is enclosed, and pins 41, 42, 43 and 44 to each ofwhich two adjacent bars are pivotally connected. More complex shapes canbe certainly obtained using more bars.

The fiber mesh 51 is a braided/overlay of multiple fibers 57 thatprovides rigidity to the morphing device 40. The fiber mesh 51 may beformed of steel fibers, composite fibers such as kevlar or zylon,aluminum fibers, or other fibers known in the art with high tensilestrength. The fiber mesh 51 may also have varying tensile strengthacross the morphing device 40. The fiber mesh can be embedded within thematrix material 52, overlaid above or underneath the matrix material 52,or enclose the matrix material 52. The fiber mesh 51 may have a uniform,patterned, diverse, or varying fiber angle distribution. Maximum widthof the morphing device is dependent upon the density distribution of thefibers. Also the density of the fibers or the number of fibers persquare inch area of the morphing device 40 may be diverse depending onthe location of the morphing device on the aircraft.

The matrix material 52 can be any material known in the art whoseelastic deformability can be significantly altered by a controllablestimulus. While all suitable stimuli can be used, such as electrical,light and magnetic stimuli, the most preferred stimulus is the change inthe temperature of the matrix material induced by a heating/coolingelement 62. One or more temperature sensors 61 are provided to allowaccurate monitoring of the temperature of the matrix material 52. Onepreferred material for use as matrix material is a shape memory polymerknown by the trademark VERIFLEX®, produced by CRG Industries, LLC. Usingthermal stimuli, shape memory polymers can exhibit a radical change froma rigid polymer to a very elastic state, then back to a rigid stateagain. In its elastic state, it will recover its “memory” shape if leftunrestrained. However, while pliable it can be stretched, folded orotherwise conformed to other shapes, tolerating up to 200% elongation.While manipulated, the shape memory polymer can be cooled and thereforereturned to a rigid state, maintaining its manipulated shapeindefinitely. This manipulation process can be repeated many timeswithout degradation. The shape memory polymer known by the trademarkVERIFLEX® is preferred at least in part due to its large range ofcustomizable thermal activation temperature (−30° C. to 260° C.).Extremely high temperatures and cryogenic ranges may be possible.

VERIFLEX® is the registered trademark for CRG, Inc.'s family of shapememory polymer resin systems which function on thermal activation atfrom −30° C. to 260° C. (−20° F. to 500° F.). Using thermal or otherstimuli, the shape memory polymers can exhibit a radical change from arigid polymer to a very elastic state then back to a rigid shape again.In its elastic state, it will recover its “memory” shape if leftunrestrained. However while pliable it can be stretched, folded orotherwise conformed to other shapes, tolerating up to 200% elongation.VERIFLEX® when heated above its transition temperature becomes elasticand can be manipulated into a different shape and then cooled tomaintain the new shape in a rigid state. When reheated above itstransition temperature, it will return to its memory shape ifunrestrained (see http://www.crgrp.net/veriflex.htm).

Although in FIG. 1, for simplicity, a single geometric morphing device40 is shown for a single airfoil member 14, the apparatus, system andmethod may utilize multiple airfoil members each of which havingmultiple morphing devices. The airfoil preferably comprises one or morerigid members 50 for providing enhanced structural integrity. Since themorphing device 40 is rendered substantially deformable while undergoinga morphing process, it is highly desirable to incorporate one or morerigid members into the airfoil member to maintain the overall structuralintegrity of the airfoil member.

The method of accomplishing the geometric morphing is illustrated inFIGS. 2 and 3.

FIG. 2 shows a morphing device 40 in an unaltered form, i.e., a steadystate condition. The composite comprising the fiber mesh 51 and thematrix material 52 is supported by four bars. For example, in therectangularly shaped morphing device 40, two long bars 82 and 84 withlength L and two short bars 81 and 83 with length b are provided. Pins41, 42, 43, and 44 are used to connect the ends of each bar to the twoneighboring bars and the four bars are allowed to pivot at thejunctures. The fiber mesh 51 is attached, at the ends of the fibers 57,to the bars. Each fiber has an initial tension T. The area defined bythe rectangular morphing device is A1=b·L.

When morphing is desired, the temperature of the matrix material isadjusted, by the heating/cooling element 62, to a value wherein thematrix material changes from a substantially rigid solid form to adeformable form with enhanced elasticity.

When the desired temperature has been achieved and the matrix materialis softened, mechanical manipulation of the bars by the motor/actuatoris relied upon to change the shape/size of the morphing device. Arepresentative morphing is accomplished by the displacement of theright-hand side vertical bar 81 in an embodiment linearly, such asdownward (shown as the direction of the arrow 3 in FIG. 2). The downwardmovement by bar 81 causes a rotation of the upper and lower bars, 82 and84 respectively, to pivot about the left-hand side vertical bar 83 toachieve the parallelogram. During the rotation, the pins 44 and 43 donot move, while the pins 41 and 42 move downward along with theright-hand bar 81. When the desired shape/size of the morphing device isachieved, such as the parallelogram shown in FIG. 3, the temperature ofthe matrix material is returned to its pre-morphing level, and thematrix material hardens and keeps the morphing device in its new form.In the morphed state shown in FIG. 3, an angle α is shown, which islarger than 0° but less than 90° and swept by the bars 82 and 84 duringthe rotation. Not only the morphing device possesses a new shape, butalso it occupies a different area, which is A2=b·L·cos(α). The ratio ofthe two areas R=A2/A1 equals cos(α). To achieve an adequate reduction ofarea, the ratio R is desired to be equivalent to ½, requiring an angleof α=60°. It is to be noted that the morphed shape is a backward sweptwing plan form and a forward swept wing plan form can be easily achievedby moving the right-hand bar 81 upward while and rotating bars 82 and 84relative to the bar 83. Furthermore, tension in the fibers is stilluniformly distributed and no substantially increase in tension isincurred compared to the pre-morphing state illustrated in FIG. 2.

While only one motor/actuator 20 is shown in FIG. 1 coupled to thesingle morphing device 40, more than one motor/actuator can be used tooperate on more than one position of the morphing device, resulting in amore accurate control or accomplishing a more complicated shape. Byusing multiple motors/actuators or one motor/actuator with more than onecontrolled connection to the morphing device, unlimited number ofmorphed shapes can be achieved. For example, as shown in FIG. 4, a Deltawing shape can be produced from a rectangular-shaped wing shape.Compared to the morphing device shown in FIG. 2, the morphing device inFIG. 4 comprises two additional horizontal bars 85 and 86, twoadditional pins 45 and 46 and an additional vertical bar 87 (partsequivalent to those shown in the embodiment in FIGS. 2 and 3 are notshown for the sake of clarity). The two pins 45 and 46 and theadditional bar 87 are located in the middle of the morphing device,together dissecting the fiber mesh and matrix into two sections. TheDelta wing can be accomplished by moving the middle bar 85 upward(direction shown by arrow 4) while simultaneously move the right-handbar 81′ downward (direction shown by arrow 5).

The above-described steps in the above methods are meant to be anillustrative example; the steps may be performed synchronously,continuously, or in a different order depending on the application.

The apparatus, system and method may be applied in a rotary aircraft,whereby a forward moving rotary blade has a different shape than aretreating rotary blade, for improved lift distribution. The apparatus,system and method may also be used to minimize rotor noise duringdynamic operation.

The apparatus, system and method may also be applied to a canard rotorwing aircraft to reverse an airfoil and increase or decrease span of acanard rotor to improve performance during a vertical lift mode or hovermode and during a fixed wing mode or cruise mode.

The apparatus, system and method provides an airfoil member that iscapable of being significantly altered in size and shape to provideincreased performance throughout one or more flight envelopes. Theapparatus, system and method is capable of improving performance of anaircraft at multiple flight speeds including at lower speeds by changingstall speed and lift of an airfoil member and at higher speed byreducing drag while maintaining optimal lift.

The above-described apparatus and method, to one skilled in the art, iscapable of being adapted for various applications and systems known inthe art.

1. An airfoil member altering system comprising at least one motor oractuator, a system controller, a plurality of vehicle performancesensors, at least one temperature controller and an airfoil membercomprising at least one geometric morphing device that is adjustable inboth size and shape, wherein said at least one morphing device includesa matrix material comprising a shape memory polymer, a high tensilestrength fiber mesh embedded in the matrix material to form a fibermesh-matrix material composite, and four bars externally located andinter-connected at their ends by a pivot, said fiber mesh-matrixmaterial composite being attached to said bars.
 2. An airfoil memberaccording to claim 1 wherein said airfoil member further comprises oneor more rigid members for providing enhanced structural integrity.
 3. Anairfoil member according to claim 1 wherein said system controller iselectrically coupled to said motor or actuator.
 4. An airfoil memberaccording to claim 1 wherein said sensors are for monitoringtemperature, pressure, velocity, acceleration, movement and attitude. 5.(canceled)
 6. An airfoil member according to claim 1 wherein more thanone morphing device is present and more than one motor or actuator ispresent, wherein each of the more than one morphing devicesindependently controlled by a corresponding one of the more than onemotor or actuator.
 7. (canceled)
 8. An airfoil member according to claim1 wherein said at least one temperature controller is coupled to atleast one temperature sensor embedded in said morphing device and atleast one heating and cooling element embedded in said morphing device.9. (canceled)
 10. (canceled)
 11. An airfoil member according to claim 1wherein said matrix material and said fiber mesh are formed from amaterial whose elastic deformability can be significantly altered by acontrolled stimulus.
 12. (canceled)
 13. (canceled)
 14. An airfoil memberaccording to claim 1 wherein said fiber mesh comprises fibers havingends, the ends being attached to the bars.
 15. An airfoil memberaccording to claim 1 wherein an increase in temperature up to athreshold causes said shape memory polymer to become more elastic, uponlowering the temperature of said shape memory polymer below thethreshold temperature, it solidifies back to a solid form.
 16. Anairfoil member according to claim 1 wherein said matrix material has anelastic deformability which can be significantly altered by acontrollable stimulus.
 17. An airfoil member according to claim 16wherein the stimulus is a change in the temperature of the matrixmaterial.
 18. An airfoil member altering system for modifying the shapeand size of the airfoil member to provide increased adaptability tovarious flight conditions throughout a flight envelope comprising anairfoil member according to claim
 1. 19-25. (canceled)
 26. An airfoilmember altering system comprising at least one motor or actuator, asystem controller, a plurality of vehicle performance sensors, at leastone temperature controller and an airfoil member comprising at least onegeometric morphing device that is adjustable in both size and shape,wherein said at least one morphing device includes a matrix materialcomprising a shape memory polymer, a high tensile strength fiber meshembedded in the matrix material to form a fiber mesh-matrix materialcomposite, said matrix material and said fiber mesh being formed from amaterial whose elastic deformability can be significantly altered by acontrolled stimulus, and four bars externally located andinter-connected at their ends by a pivot, said fiber mesh-matrixmaterial composite being attached to said bars, and each of said atleast one morphing device is independently controlled by a correspondingone of said at least one motor or actuator.
 27. An airfoil memberaccording to claim 26 wherein said airfoil member further comprises oneor more rigid members for providing enhanced structural integrity. 28.An airfoil member according to claim 27 wherein said system controlleris electrically coupled to said motor or actuator.
 29. An airfoil memberaccording to claim 28 wherein said sensors are for monitoringtemperature, pressure, velocity, acceleration, movement and attitude.